There is a desire to unravel the molecular composition of multi-component polymer systems such as, for example, propylene-based impact copolymers and other polyolefin polymer blends. Here and throughout this specification, polymer blends comprising at least two distinct polymers will be referred to as a multi-component polymer, or “MCP”, and preferably is a propylene-based impact copolymer comprising a continuous propylene homopolymer phase and discontinuous domains of ethylene-propylene copolymer or rubber. In any case, the conventional rubber extraction method, which includes xylene solvent extraction in conjunction with other composition characterization techniques, has been used for decades in order to independently study the crystalline and the rubber phases of MCP. However these approaches are usually inefficient and frequently result in reproducibility issues.
PolymerChar™ Gel Permeation Chromatographs (“GPC”) and other chromatographic equipment equipped with one or more band-filter based multi-channel infra-red (“IR”) detectors have been demonstrated to provide a powerful technique for MCP characterization due to high detector sensitivity, simultaneous measurement of molecular weight and ethylene-derived units (“C2”) of the polyolefin, and fast turnaround time. In previous studies of MCP's, a series of methodologies had been developed with GPC-IR to deconvolute the MWD (Mw/Mn, where Mw is the weight average molecular weight, and Mn is the number average molecular weight) of crystalline phase and rubber phase. However the weakness with this approach is that additional information is needed to perform the deconvolution, and the MCP is modeled as a simple binary system of a mixture of PP and EP. Recent studies have revealed that most MCP's are not a simple binary mixture of polymers and typically include more detailed structure such as atactic polypropylene and polyethylenes.
The present invention(s) introduce a more advanced method to study both the major phases and minor phases of MCP's by integrating GPC-IR characterization with simple fractionation. This method can directly provide information on the amount of EP (ethylene-propylene copolymer or rubber, and polyethylenes, PE) and the C2 levels in each without any additional information. The composition and the MWD of each phase will also be provided.